Medical procedures involving access to the brain through a burr hole in the skull are used to treat a variety of medical conditions. For example, electrical stimulation of the brain to relieve chronic pain, or for the treatment of movement disorders, may necessitate access via a burr hole. Similarly, burr holes are typically formed to allow implantation of a catheter, e.g., an intraparenchymal (IPA) or intracerebroventricular catheter, to treat various ailments.
Use of a catheter to deliver a therapeutic agent to the brain generally involves the insertion of the catheter into the brain and dispensing the agent at the desired location. During a typical implantation procedure, an incision may be made in the scalp to expose the patient's skull. After forming a burr hole through the skull, the catheter may be inserted into the brain. To accurately place the catheter and avoid unintended injury to the brain, surgeons typically use stereotactic apparatus/procedures. One exemplary stereotactic apparatus is described in U.S. Pat. No. 4,350,159 to Gouda, which may be used to position, for example, an electrode.
As one can appreciate, once an inserted device such as a catheter is properly positioned, it is important that it be adequately immobilized to prevent movement of its distal, therapy delivering tip from its intended location. Even minimal movement of the device tip may reduce therapeutic efficiency. Accordingly, reliable methods and apparatus for anchoring and securing the device relative to the burr hole are desirable.
In typical implantations, a proximal end of the device (e.g., a therapy catheter) may extend out of the burr hole and be anchored at the burr hole with an anchoring device. The free end of the therapy catheter may then be tunneled beneath the skin and connected to a secondary delivery catheter that is, in turn, coupled to a source (e.g., an implanted infusion pump) containing the therapeutic agent. As a result, the agent may be delivered through the delivery catheter and the therapy catheter to the desired location within the patient. As one may appreciate, the two catheters may require accurate pre-sizing (prior to implantation) to ensure that their respective coupling ends are ultimately proximate one another prior to connection.
During and after implantation, various bodily forces may act on portions of the therapy catheter that extend outside of the burr hole. Depending on the anchor design, these forces could be sufficient to eventually shift the therapy catheter, and thus its distal end, away from the desired location. Even slight forces applied to the therapy catheter may result in shifting of its distal end. For example, bodily induced forces such as those resulting from patient movement, forces transferred through the scalp, or changes in the surrounding tissue (e.g., swelling), may result in movement of the therapy delivery catheter.